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Gladiolus Diseases

Disease

Symptoms

Pathogen/Cause

Management

Botrytis Blight

Brown spots that may have reddish margins develop on leaves. Spots can be very small to over 1/2 inch in diameter. Similar spots on stems become soft and rot in wet weather. Small, clear spots on petals become brown. A neck rot may occur at the soil line. Small black granules (sclerotia) form on the surface of the infected corms.

Botrytis gladiolorum

Do not plant infected corms. Purchase corms that were treated with hot water and fungicides. Apply a fungicide to protect plants.

Curvularia Leaf Spot

Long, rectangular spots on leaves are tan with a brown margin and yellow halo. Concentric rings form within the enlarging spots. Corms rot.

Curvularia trifolli f. sp. gladioli

Do not plant infected corms. Plant in pasteurized soil. Apply a fungicide to protect plants.

Fusarium Yellows

Roots have brown spots or general rot. Older leaves yellow. Flower size, shape and color may be abnormal. Flowers may not develop while stalks are curved in an S-shape. Corms rot from the center outward. Oval, sunken spots on the corm surface are brown and may have concentric rings.

Fusarium oxysporum f. sp. gladioli

Do not plant infected corms. Maintain a soil pH of 6.6-7.0 and use nitrate as the nitrogen source when fertilizing.

Nematodes

Root system is small. Plants are stunted and flower late. Galls may form at nodes. Fusarium yellows may be severe.

Plant in soil that has been steamed or chemically pasteurized. Maintain good weed control.

Scab

Brown, round, sunken areas with raised edges are on corms. A soft rot of the neck develops.

Pseudomonas marginata

Do not plant infected corms. Disinfest cutting knives frequently. Maintain good mite and insect control. Water in a manner that keeps leaf surfaces dry. Avoid working on wet plants.

Stemphylium Leaf Spot

Small, round yellow spots have a distinct reddish center when held up to the light. Mature leaves have the most spotting.

Stemphylium botryosum

Apply a fungicide to protect plants.

Stromatinia Dry Rot

Corm scales are brown and may appear shredded. Small reddish-brown spots on the surface of the corm can be removed, leaving a clean, shallow, sunken area. Corms are dry, hard, and mummified. Clusters of plants are killed by neck rot.

Stromatinia gladioli

Do not plant infected corms. Purchase corms that have been treated with hot water and fungicides. Plant in soil that has been pasteurized. If infection is noted after planting, Apply a fungicide to protect plants.

Viruses

Flowers are small, distorted or have color breaking. Leaf tissue may be mottled, have white flecks, or reddish blotches.

Maintain good insect control. Plant in pasteurized soil free of nematodes and weeds. Destroy infected plants as soon as they are found.

Fusarium yellows.

Scab.

Cucumber mosaic virus symptoms on leaves and flowers.

Prepared by Gary W. Moorman, Professor of Plant Pathology

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